1. Field of the Invention
The present invention relates to a high speed shear for transverse cutting of rolled strips, in particular, very thin strips, and including two, oppositely located drums, at least one blade having a cutting edge and provided on one of the two drums, with the blade being accelerated to the displacement speed of the to-be-cut strip, and a controllable device for displacing the two drums between a cutting position, in which the strip is cut, and an open rune-through position in which the strip can be freely advanced between the drums.
2. Description of the Prior Act
A shear of the type described above is disclosed, e.g., in German Patent No. 475,512. In the disclosed shear, the blades are connected with respective drums by levers and cooperate each with a cam disc, which is fixedly secured on a shaft of a respective drum, in such a manner that the blades do not circulate radially but are displaced parallel to each other and transverse to the rolled stock, with the rolled stock being cut, as with a stationary shear, usually across.
With such a drum shear, as with a drum shear with a circular rotation of the blades, the formation of needle-shaped burrs cannot be satisfactory prevented and, moreover, in many cases, the cut is incomplete.
U.S. Pat. No. 5,207,138 discloses a high-speed shear for transverse cutting of a strip material and having upper and lower blade drums which are displaced away form each with a hydraulic setting device and which are accelerated until the rotational speed of the drums corresponds to the advancing speed of the to-be-cut rolled strip. Then, the drums are brought into their cutting position and shear the strip. The drums are driven by a single motor via a divider mechanism. The drive includes a rotational position sensor for generating positional signals in response to which, a control device controls the approachment movement of the drums until the drums are brought into their cutting position. The drive, gear, transmission, control, and setting parts of this shear are rather expensive.
Another high-speed shear for transverse cutting of rolled strips is disclosed in German application DE 198 09 813A. The shear is designed for quality cutting of very thin strips advanced with a speed up to 3 m/sec. One of the drums is supported on a rocker arm, and the adjusting or setting device includes a drive, which provides for a cutting movement of the drum, and support element arranged between the drive and the rocker arm, with the support element being shortened in accordance with the operative position of the cut. The cutting tools are formed as a chisel provided on one of the drums and an anvil provided on another drum.
German Publication DE-OS 26 54 866 discloses a rotary drum shear for extruded rolled stock. The shear includes a drum rotating device with force-transmitting means connected with one of the drums, and a drive for continuously rotating the drums with speeds that provide for synchronization of tangential speed of the shear blades with the running speed of the cut material. The shear further has a drum adjusting or setting device including a further drive for displacing the shear drums between an open, run-through position, and a cutting position. The shear also includes a control unit for the drive of the adjusting or setting device which controls the drive operation.
In the shear disclosed in DE-OS 26 54 866 the ratio of the diameters of the first and second drums in equal 2 to 3, and their rotation is so coordinated that the second drum performs two revolution per three revolution of the first drum. The drum setting or adjusting device is so controlled that the first and second drums are in the cutting position after six revolutions of the first drum and four revolution of the second drum.
In the shear of DE-OS 26 54 866, a very precise positioning of the blades is required in order to obtain a smooth, burr-free cut of the strip which, in turn, requires precise mounting of the drive elements in order to obtain a backlash-free operation. Besides, the drive elements, the control unit, various setting and adjusting devices are rather complicated and are, therefore, very expensive.
Accordingly, an object of the present invention is to provide a high-speed drum shear for transverse cutting of a rolled strip and, in particular a very thin strip, in which the above-listed drawbacks are eliminated.
Another object of the present invention is to provide a high-speed drum shear for transverse cutting of a rolled strip with reduced constructive expenses of elements used in synchronization of the drums, while insuring an exact positioning of the blades during the cutting process.
This and other objects of the present invention, which will become apparent hereinafter, are achieved by providing in a high-speed shear of the type described above, a device for rotationally synchronizing the two drums in both their open position and their cutting position, with the synchronizing device having respective tooth elements provided on the two drums and engaging each other, and with the tooth elements being so formed that they insure synchronization in the open position of the drums when they engage each other with a large tooth backlash and, in the cutting position of the drum, engage each other substantially backlash-free. Advantageously, the tooth elements are formed with involute teeth.
Providing a device according to the present invention, which insures a permanent synchronization in both the open position of the drums when the drums are spaced from each other, and the cutting position of the drums, permits to eliminate the additional divider mechanism for transmitting the rotational movement to both drums, together with the necessary to that end double universal joint shafts. Eliminating such divider mechanism substantially reduce manufacturing, maintenance and exploitation costs. In addition, a correct tooth backlash in the cutting position or actually its absence, except of a very small backlash necessary for obtaining a precise blade gap, is positively obtained. With an increase of the distance between the drums, the backlash also positively increases. However, under all conditions, independent on the size of the backlash, synchronization is insured to an extent that permits to transmit the necessary idle-run torque.
According to the present invention, one of the drums has a fixed support, and another drum has an adjustable support. Advantageously, the adjustment or setting of the adjustable support is effected by using an eccentric support with a controllable drive. Preferably, both drums have adjustable, mechanically driven, eccentric supports, with the supports being synchronized with a gear mechanism.
Further, in order to insure a balanced drive of both drums, with one drum being a driving drum and another drum being a driven drum and with a smallest possible tooth backlash, the one drum is provided with a rotary drive having an electromotor, and another drum is provided with a brake, advantageously, an electric brake.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.